The present invention relates to a seat and holding valve.
In water hydraulic engineering, it is very important for a holding valve to be leakproof in the holding operation. Leakages under high pressures of, for example, 300 bars lead to the destruction of the valve within few seconds.
For this reason, it is very important in water hydraulic engineering that a high accuracy be applied in the manufacture of the seat pairing of a valve. This means that the valve seat must be accurately adapted to the valve cone with the least tolerances. This includes not only consistency with respect to the cone angles, but also congruence with respect to the cone axes of the valve seat and the valve cone. While on the one hand this high precision in the manufacture is difficult to realize and difficult to reproduce, it is also very expensive on the other hand.
It is accordingly an object of the invention to provide an absolutely leakproof holding valve, which is largely independent of the manufacturing tolerance and can therefore be manufactured with a good reproducibility and at little cost, and which can operate free of wear and trouble, and yet be robust and reliable.
The present invention solves the above and other problems by providing an improved hydraulic seat and holding valve for hydraulically controlling and for holding a hydraulic load. The improved valve comprises a valve piston supported in a valve housing for pivoting relative to a generally conical valve seat of the valve housing. The valve housing at least partially defines a first chamber and a second chamber, and the valve seat is positioned between the first chamber and the second chamber. The valve piston comprises a generally conical circumference that can be characterized as a valve cone. The valve cone and the valve seat function together as a seat pairing for closing the first chamber relative the second chamber to hold the hydraulic load in a substantially leakproof manner. This development has the advantage that it results in a hydraulic load-dependent sealing, so that even a high load does not lead to leakage.
The valve preferably further comprises a valve shaft positioned in the valve housing. In accordance with a first embodiment of the present invention, the valve cone is mounted to the valve shaft for swinging movement relative to the valve shaft. In this case the means for mounting the valve cone to the valve shaft comprises an elastic seal positioned between the valve cone and the valve shaft.
In accordance with a second embodiment of the present invention, which is advantageously applicable to any type of seat valve, the valve piston is fixedly mounted to the valve shaft, to form an inflexible unit therewith, while the valve shaft has a lateral play at its guiding end, which is one of the ends opposite the valve cone, to permit pivoting of the unit in the valve housing.
In accordance with one version of the second embodiment, the guiding end of the valve shaft is sized so that there is lateral play between the guide end of the valve shaft and the valve housing, so that the valve shaft is adapted for pivoting in the valve housing. This development permits guiding the valve cone in a safe manner and handling high pressures, while simultaneously ensuring the pivotal capability of the valve cone, so that a uniform face pressure results in the seat pairing.
In accordance with another version of the second embodiment, the guiding end of valve shaft is guided in a guiding member preferably without lateral play while the guiding member is sized with respect to the valve housing to permit lateral play therebetween. This development permits guiding the valve cone in a safe manner and handling high pressures, while simultaneously ensuring the pivotal capability of the valve cone, so that a uniform face pressure results in the seat pairing.
The valves of the various embodiments of the present invention are useful, for example, when they are under a high hydraulic load, which must be kept leakproof. This load can act upon a cylinder-piston unit, for example, from the outside, but can also be exerted by a pump, which connects to a plurality of consumers, so that the valve has to hold a continuous load.
In accordance with one aspect of the present invention, the cone angle of the valve seat and the cone angle of the valve cone are made different. Preferably, the difference is from approximately 2.5xc2x0 to 8xc2x0. This results in a circular line contact, which leads to a high face pressure, so that the valve cone and valve seat optimally adapt to each other.
Preferably, the cone angle of the valve cone is smaller than the cone angle of the valve seat.
Other aspects of the present invention further provide degrees of freedom of the valve shaft that facilitate desired pivotal movement of the valve shaft.
In accordance with another aspect of the present invention, the valve is a combination of a holding valve and a control valve.